Navigation method and a navigation system for determining a route for a means of transport moving from starting point to a destination

ABSTRACT

A navigational method and a navigational system for determining a route from a starting location to a destination location for a means of locomotion, especially for a motor vehicle, an airplane, or a ship, the route being calculated on the basis of a digital database, which contains predetermined path segments Wi having correspondingly assigned nodal points Ni, which connect the specific path segments Wi to each other, the specific weightings Gi being assigned to the path segments Wi and/or to the nodal points Ni. In this context, the weightings Gi that are used for the route calculation are varied as a function of the time of day.

FIELD OF THE INVENTION

The present invention relates to a navigational method for determining a route from a starting location to a destination location for a means of locomotion, especially for a motor vehicle, an airplane, or a ship, the route being calculated on the basis of a digital database, which includes predetermined path segments W_(i) having correspondingly assigned nodal points N_(i), which connect individual path segments W_(i) to each other, specific weightings G_(i) being assigned to path segments W_(i) and/or nodal points N_(i). The present invention also relates to a navigational system for determining a route from a starting location to a destination location for a means of locomotion, especially for a motor vehicle, an airplane, or a ship, a digital database being provided for calculating the route, the database including predetermined path segments W_(i) having correspondingly assigned nodal points N₁, which connect individual path segments W_(i) to each other, specific weightings G_(i) being assigned to path segments W_(i) and/or nodal points N_(i).

BACKGROUND INFORMATION

Navigational systems, such as those that operate on the basis of GPS (Global Positioning System), support an operator of a means of locomotion in navigating to a predetermined destination. In this context, the navigational system determines an optimal path, i.e., an optimal route, at least on the basis of starting and destination coordinates and of a corresponding digital database, which is essentially an image of the real street network and is also designated as a digital map. Conventional navigational systems calculate a route between two points taking into account previously defined average speeds, which are stored permanently for each street type that is present in the digital map. In any case, just as with PC-based route search programs, individual direction values can be defined by the user for the street classes, but these direction values often do not rest on true average values but rather on the assumptions of the user. Recently, it has become possible to adjust these speeds on the basis of the instantaneous traffic situation, which is termed “dynamic navigation.” However, these systems are cumbersome and expensive because they require a data connection from the navigational system to a telematic central office.

SUMMARY OF THE INVENTION

It is an object of the present invention to make available an improved navigational method of the type cited above as well as to make available an improved navigational system of the type cited above, which eliminate the aforementioned disadvantages. For this purpose, in a navigational method of the aforementioned type, it is provided in accordance with the present invention that weightings G_(i) that are used for the route calculation are varied in accordance with the time of day.

This has the advantage that the weighting of a street that is represented in a digital map is no longer constant but is viewed, or determined, as a function of time. In this way, by taking account of the fluctuations in the traffic density according to the time of day, more realistic data can be achieved for a calculated, anticipated duration of driving. In addition, the calculated route is adjusted to a specific time of day, because at the main traffic times, the main traffic routes are more significantly affected by a reduction in possible average speed than subsidiary routes.

For example, for each path segment W_(i) two weightings G_(i) are used for two times of day, or weightings G_(i) as a function of time t are determined as G_(i)(t).

In one preferred embodiment, weightings G_(i) are calculated from the product of G_(i)=L_(i)*K_(i), L_(i) being a length of path segment W_(i), and K_(i) being a path segment class that is proportional to the average speed that is possible on path segment W_(i). To vary weightings G_(i), path segment class K_(i), which is assigned to this path segment W_(i), is varied in accordance with the time of day.

A simple function for switching over between day and night conditions is achieved as a result of the fact that for each path segment W_(i) two path segment classes K_(i) for two times of day are used. This simple function has the advantage that the corresponding value only has to be calculated once before the beginning of the route calculation, and the route calculation then proceeds as if using a constant weighting. Alternatively, path segment class K_(i) as a function of time t is determined as K_(i)(t).

In a navigational system of the above-mentioned type, according to the present invention, variable weightings G_(i) are provided as a function of the time of day.

Thus, for example, for each path segment W_(i) two weightings G_(i) for two times a day are provided, or a predetermined function of time t is provided, which varies the weightings G_(i) as a function of time, yielding G_(i)(t).

In one preferred embodiment, weightings G_(i) correspond to the product of G_(i)=L_(i)*K_(i), L_(i) being a length of path segment W_(i), and K_(i) being a path segment class that is proportional to the average speed that is possible on path segment W_(i). To vary weightings G_(i), in this context, path segment classes K_(i), which are assigned to this path segment W_(i), are provided as a function of the time of day.

A simple function for switching over between day and night conditions is achieved as a result of the fact that for each path segment W_(i) two path segment classes K_(i) for two times of day are provided. This simple function has the advantage that the corresponding value only has to be calculated once before the beginning of the route calculation, and the route calculation then proceeds as if using a constant weighting. Alternatively, a predetermined function of time t is provided, which varies path segment class K_(i) as a function of time, yielding K_(i)(t).

BRIEF DESCRIPTION IF THE DRAWING

The FIGURE depicts a block diagram of a preferred embodiment of the navigational system according to the present invention.

DETAILED DESCRIPTION

The concrete realization of the present invention in a navigational system depends on the type of algorithm used for the route calculation. In the preferred embodiment of the present invention described below, it is assumed only by way of example that weighting G_(i) of a path segment, or route section, W_(i) is proportional to a path segment, or street class, K_(i) and to a length L_(i) of this path segment. Weighting G_(i) of path segment W_(i) is then determined by the product of

G_(i)=L_(i)*K_(i).

For the shortest segment, K_(i)=1 is assumed, and sum G is minimized. For the fastest segment, K_(i) is inversely proportional to the speed that is possible on section, or path segment, W_(i). For example, K_(i) is measured in s/km (seconds per km). According to the present invention, two K_(i) tables for two different times of day are then provided. The times a day are, for example, from 7:00 a.m. until 7:00 p.m. (day) and from 7:00 p.m. until 7:00 a.m. (night). In accordance with the instantaneous clock time, street class K_(i) is then derived from a K_(i) ^(7am-7pm) table or from a K_(i) ^(7pm-7am) table. Alternatively, weighting G_(i) is determined as a function of time t according to the formula

G_(i)(t)=L_(i)*K_(i)(t).

The latter has the advantage that in a more powerful system, the main traffic times can also be taken into account as fluctuations in traffic density occurring in accordance with the time of day. The corresponding progress lines are known as average values for most streets, and they therefore function as the basis for a “universal” characteristic curve K_(i)(t).

In the following description of one preferred embodiment of the present invention on the basis of the single FIGURE, the assumption is made of the first case, in which the times of day are divided into “day” and “night.” At 10, the navigational system starts the navigational process, and at 12 an initialization takes place, in that a user inputs a destination point. The starting point is automatically determined at 14 as the instantaneous location, for example, using GPS (Global Positioning System, i.e., a satellite navigational system). In addition, the time of day is determined. In block 16, a check is carried out as to whether the time lies between 7:00 a.m. and 7:00 p.m. If it does, the process is continued through branch 18, and in 20 a route based on the day values of weightings G_(i)(day) is calculated using street classes K_(i) from the K_(i) ^(7am-7pm) table. If it does not, then the process is continued to branch 22, and in 24 a route based on the night values of weightings G_(i)(night) is calculated using street classes K_(i) from the K₁ ^(7pm-7am) table. In block 26, the guidance system mode begins, in which the user is guided by optical and/or acoustical signals, or commands, along the calculated route.

In block 28, for example, each time a nodal point N_(i) is reached between two path segments W_(i) and W_(i+l), a check is carried out as to whether the destination has been reached. If not, then the process is continued through branch 30, and in block 32 the instantaneous position is determined, for example using GPS, along with the street class and the time, and then once again guidance system mode 26 is executed. If the check in 28 yields a “yes,” then the process continues through branch 34, and in 36 the user is informed that the destination location has been reached. In addition, the navigational mode is terminated. In block 38, finally, navigational method ends. 

What is claimed is:
 1. A navigational system for determining a route from a starting location to a destination location for a locomotion device, comprising: an arrangement for providing a digital map base for calculating the route, the digital map base including predetermined path segments W_(i) having correspondingly assigned nodal points N_(i) that connect the predetermined path segments W_(i) to each other; and an arrangement for assigning specific weightings G_(i) to at least one of the predetermined path segments W_(i) and the nodal points N_(i), wherein: the specific weightings G_(i) vary as a function of a time of day, and the specific weightings G_(i) correspond to a product of G_(i)=L_(i)*K_(i), L_(i) being a path segment length, and K_(i) being a path segment class K_(i) that is inversely proportional to an average speed that is possible on one of the predetermined path segments W_(i).
 2. The navigational system according to claim 1, wherein: the locomotion device includes one of a motor vehicle, an airplane, and a ship.
 3. The navigational system according to claim 1, wherein: for each path segment W_(i) two weightings G_(i) for two times of day are used.
 4. The navigational system according to claim 1, further comprising an arrangement for providing a predetermined function of a time t, the predetermined function varying the specific weightings G_(i) as a function of time to yield G_(i)(t).
 5. The navigational system according to claim 4, further comprising: an arrangement for providing another predetermined function of the time t, the other predetermined function varying the path segment class K_(i) as a function of time to yield K_(i)(t).
 6. The navigational system according to claim 1, further comprising: an arrangement for, for varying the specific weightings G_(i), providing the path segment class K_(i) that is assigned to the corresponding predetermined path segment W_(i) and that is a function of the time of day.
 7. The navigational system according to claim 1, further comprising: an arrangement for providing two path segment classes K_(i) for two times of day for each predetermined path segment W_(i). 